Process of preparing nitrogen compounds.



C. KRAUSS & P. STAEHELIN.

PROCESS OF PREPARING NITROGEN COMPOUNDS.

APPLICATION FILED DEC. 6, 1913. RENEWED DEC. 8, 1916.

1,212,50. Patented Jan. 16, 1917.

2 SHEETS-SHEET I. i

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i! k w C. KRAUSS & P. STAEHEUN.

PROCESS OF PREPARING NITROGEN COMPOUNDS.

APPLtCATION FILED DEC. 6, 1913. RENEWED DEC-8.1916.

1 21 2,50%, Patented Jan. 16, 1917.

2 SHEETSSHEET 2.

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CONSTANTIN KRAUSS, 0F COLOGNE-BRAUNSFELD, AND PAUL STAEHELIH, 01F KNAPSACK, NEAR CQLQGNE, GERMANY.

rnocnss or rnnranmc NITROGEN COMPOUNDS.

21,212,5lld.

Application filed December 6,

To all whom it may concern:

Be it known that we, CONSTANTIN Knivesand PAUL STAEHELIN, subjects of the King of Prussia, German Emperor, and residents at Cologne-Braunsfeld and Knapsack, near Cologne, respectively, in the Province of the Rhine, Kingdom of Prussia, German Empire, have invented a certain new and useful Process of Preparing Nitrogen Compounds, of which the following is a specification.

lhis invention relates to a process and apparatus for the production of nitrogen compounds.

It is already known: (1) To produce nitrogen compounds from metallic carbide or carbid mixtures and nitrogen in a continuous operation (see Norwegian Patent No. 20777, Italian Patents Nos. 112336 and 101994, also German Patents Nos. 7911 and 1 19594 and so forth). (2) That on the reaction of nitrogen upon the carbid, certain limits of temperature must be maintained because the reaction is reversible (see Caro and others, Zeitschrift fii r EZe/ntrcchemic 1909, S. 1179; Le Blane, Zeitschrift ft'ir EZek-rochcmic 19l120;' Bredig, Zeitschrift f iir EZcktmchem-ic). (3) 'l hat the reaction between ordinary nitrogen and carbid can be hastened quite materially, if the reaction takes place in the presence of certain chemical reagents especially the halogens (see latcnt Polzenius 163320). That the reaction of nitrogen with metallic carbid is strongly eXo-t-herinic. Efforts have therefore been made either by cooling or by a particular manner of the supply of nitrogen to regulate the reaction temperature (see Norwegian Patent No. 20777, United States Patent No. 100%509, German Patents Nos. 149594 and 228925. It is moreover the desire of every technician to arrange his manufacture as continuous as possible. All the above named patents have by themselves not yet been able to attain any conspicuous success in the technical industry, in this regard, for they are all of them troubled with more or less serious drawbacks. Especially there are two points which have hitherto greatly hindered the technical availability accordin? to the processes above proposed namely (13 the method of the transport of the reaction mass through the apparatus and (2) the regulation of the correct temperature.

Most inventors have overlooked that on Specification of Letters Patent.

Patented Jan. 16:, 119117..

the reaction of nitrogen upon a metallic can bid, the reaction product does not remain pulverulent, but sinters together whereby stoppages of the apparatus are inevitable; and those inventors who have grasped the importance of the regulation of the temperature have remained quite unclear over the point as to the amount of energy liberated in the reaction. lhe applicants for both the Norwe ian Patent No. 207 7 7 and the United States atent No. 1004509 which have most completely developed the temperature regulation hitherto, remain far from their goal.

lhe Norwegian patent endeavors to 18gL1-,

late the reaction heat, by conducting the nitrogen around the outside of the double walled apparatus, heating it thereby and then first allowing it to act uponthe hot carbid. Consequently, it brings together at the moment when the reaction mass possesses the highest temperature, the hottest nitrogen to react upon it, a process which must create the opposite of the purpose in view. In addition thereto, there is the fact that the released quantities of heat very greatly exceed what the quantities of nitrogen necessary for the process under normal conditions capable of taking up. The United States patent endeavors to regulate the temperature by shutting off the supply of nitrogen from time to time either par tially or entirely by automatic means. 'lhat such a method of working is only a technical trick is obvious, because with the shutting ofl of the supply of nitrogen, the entire apparatus is brought to a standstill, because otherwise under the circumstances, the carbid which is not yet treated with nitrogen would be moved by the rotation of the cylinder toward the exit, whereby neither a uniform production in regard to quantity nor yet in regard to quality could be attained without regard to the fact that the apparatus will technically not be fully utilized. The mistake which both these inventors have made is to be seen in the first instance in that theyas above stated-are not aware of the large quantites of heat which are liberated during the reaction. Both the aforesaid processes have moreover the further drawback that the reaction product escapes in a brightly incandescent condition from the apparatus and must be prepared by means of special cooling devices for further treatment. Moreover,

both the inventors overlook the fact that the brightly incandescent nitrogen product which is produced sinters together fast and the apparatus must be stopped up in a very short time.

In the following specification. we describe a process and apparatus which according to our experience, avoids the aforesaid drawbacks and enables a continuous working to take place with the. most economical utilization of the technical constructions. Our process is also based on the principle of the reaction of the nitrogen upon the carbid in counter current. and in addition the regulation of the reaction temperature at those parts of the apparatus where increases of temperature are developed.

The reaction of the nitrogen can take place in two different ways. (1) By causing both the material and also the nitrogen to move. (2) By causing nitrogen gas to act in counter current upon the stationary material.

The accompanying drawing shows a simple apparatus for carrying out the process herein described. in which Figure 1. shows a longitudinal section of a channel furnace. Fig. :2 shows a modification of the apparatus shown in Fig. 1. and Fig. 3. is a plan view on the line .I' w. of Fig.

For the first mode of working. there is employed a horizontal channel furnace (Fig. 1). This furnace consists of four parts: 1 A preliminary" heating space. 2 full heat.- ing space. 3 reaction space. and l A cooling space.

In the preliminary heating space Y the reaction product (finely pulverized carbid or carbid mixtures with or without additions which facilitate the reaction) is warmed by means of the gases escaping from the other spaces. In the heating chamber II. the carbid is heated up to the temperature necessary for the carrying out of the reaction.

In the reaction space It the ti'catn'ient withnitrogen is effected: in the cooling space K.

the finished product is cooled down until it can be withdrawn without special precau tions and can be further utilized.

The method of working is as follo\\'s: The linely pulverized material. to which substances facilitating the reaction can be added. is transported by mechanical means. such as trucks. transporting bands or the like through the furnace. in the contrary direction to that in which the material to be treated with nitrogen is transported. there is admitted cold nitrogen gas. In the preliminary heating space the excess escaping gases give up part of their heat to the material and are drawn otl comparatively cool. The material then passes somewhat warmed into the heating space. where it is heated up to the reaction temperature. either by means of an electric heating device or by outside .the- ,tiansporting is here an interchange between the cool in-- flowing nitrogen gas and the reaction masses proceeding out of the heating a kind that under action mass before space of such all circumstances, the recooliiig must exceed the critical temperature which assures the quantitative nitrogenizing and prevents any reformation of the. carbid.

As above stated. it is necessary to work witha quite extraordinarily great surplus of cold nitrogen in order to overcome by this means the masses of h at liberated. This would. however. render the process costly and moreover enablc no certain working reaction because under certain circumstances. during short interruptions of he operation. local heating can take place nich might injure the material in the furiiace or mechanism. 'e have therefore in addition to'the ternal supply of the cool nitrogen current also devised a regulation of the furnace by outward cooling. For this purpose. we have surrounded the channel furnace with an outer cooling mantle and have constructed the inner mantle froiii-niaterial which conducts heat. By this arrangement it becomes possible whenever the various measuring instrunients inserted in the reaction space iiiilicate an undesirable rise of temperature. to act immediately upon the temperature by passing cold air between the channel furnace.

and the outer mantle. in this manner therefore.- a double ten'iperature regulation takes place. lirstly by the nitrogen in the interior of the channel furnace and secondly by air and cooling at the outside. .\s the overheating (as already stated) is cliietiy local. we have arranged to allow the cold nitrogen gas to flow into the reaction space at various points to regulate temperatures. .\loreover. we ha vedividtal the cooling space between the channel furnace and the outer mantle in various divisions. as may be seen in the drawing. whereby we are inthe position to cool certain parts of the channel furnace according to requirement. From the reaction space the reacting material passes into the cooling space and is also capable of being cooled down by surrounding air so that the reaction mass can be so far cooled that its removal from the furnace and its further treatment is not hindered.

For the second method of working in which the material absorbing the nitrogen very regulatable intill is not moved but remains at the same position in the furnace until it is completely used up, a kind of ring furnace is provided, the operation of which is as follows:ln the various chambers of the furnace (Figs. 2 and 3) the carbid or the carbid mixture is spread out on stages in layers. The separate chambers R, R are provided with suitable heating devices H for electric internal heating. The nitrogen inlet takes place at various points, of the separate chambers. For the commencement of the process, there is first heated one chamber to the reaction temperature, then cooled nitrogen is passed in and in such a quantity that the same suffices to prevent the reaction temperature rising beyond the best point. For this there are obviously required much greater quantities of gas than are needed for the saturation of the carbid which is in the chamber. The unconsumed highly heated nitrogen is introduced in the second chamber and reacts upon the carbidthere. Here again, reaction heat is liberated which would lead to the overheating of the reaction product. In order to prevent this cooled nitrogen is introduced in such quantities that again the best reaction temperature is not exceeded. The nitrogen is passed through the first chamber until the mass is suiliciently cooled. This hot nitrogen passes as already stated, from the first into the second chamber. The temperature of the nitrogen passing in is lowered however in the degree that the reaction product is cooled in the first chamber, consequently the introduction of fresh cold nitrogen in the second chamber must be gradually reduced.

The same operation takes place in the third chamber again and so forth. The heating of the chambers will therefore only need to be undertaken when for some industrial reason or other, a chamber has not attained to the necessary reaction temperature or when a furnace is being newly started. As even in this mode of working, local overheatings are not impossible, we have constructed in the separate reaction chambers cooling tubes or cooling boxes K of material which easily conducts heat, through which cold air can be passed, as soon as the measuring instruments indicate an undesirable rise of temperatureit will be obvious without further explanation that firstly achoking of such apparatuses is rendered impossible, whereby a uniform action of the nitrogen is secured, and that secondly, an injurious overheating of the reaction product and a 'redecomposition of the nitrogen compound already formed is rendered impossible, because in the attaining of the most suitable reaction temperature. no overheating but rather a gradual cooling takes place in the nitrogen current, and because moreover the reaction product leaves the apparatus cooled.

According to our process there arises in the action of nitrogen on carbid, a mixture of nitrogen compounds and, in fact, chiefly calcium cyanamid, also dicyandiamid and cyanid. By proper additions we are in a position to increase the production of one of the latter products at the expense of the cyanamid.

Finally, the saving of heat is the most favorable possible because both the heat which is stirred up in the product left in the furnace is absorbed by the current of cold nitrogen gas and also the heat of the nitrogen gas which is drawn off is continuously transferred to the newly charged reaction mass, and also the reaction heat liberated during the reaction is so controlled that it cooperates to assist and not to injure the process. Saving of heat according to our process is actually so favorable that the reaction process proceeds almost entirely without the addition of heat from without when once the mass in the furnace has been brought to the requisite temperature. The heating devices then serve simply as regulators of the temperature.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is 1. A process for the continuous production of nitrogen compounds which consists in subjecting the material to be combined with nitrogen in pulverized state, to a preliminary-heating, passing the material through .a heat of reaction temperature, then passing the material to a point of critical temperature, and subsequently cooling the resultant mass, all in the path of a current of nitrogen gas flowing in a direction opposite to that of the travel of the material.

2. A process for the continuous production of nitrogen compounds which consists in subjecting carbid, in pulverized state, to a preliminary heating, passing the partially heated carbid through a heat of reaction temperature, then passing the mass to a point of critical temperature, and subsequently cooling the resultant mass, all in the path of a current of nitrogen gas flowing in a direction opposite to that of the travel of the carbid.

in testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

CONSTANTTN KRAUSS. PAlll'i STEsl-CHELTN.

Witnesses lioUIs Vannonr, Oscar DAPNER. 

